1. Field of the Invention
The present invention relates to a common channel signaling (CCS) system, and in particular to an apparatus and a method for translating a global title in a No.7 signaling network.
2. Background of the Related Art
Generally, a common channel signaling is a signaling method for transmitting a signal about a call through a signaling line that is separate from the traffic line.
FIG. 1 is block diagram illustrating a No. 7 signaling network as an example of one CCS methods. As depicted in FIG. 1, a signaling point of the No.7 signaling network is divided into a signaling end point (SEP) A, F and a signaling transfer point (STP) B, C, D, and E.
FIG. 2 is a block diagram illustrating a protocol stack of each signaling point of the No.7 signaling network.
A protocol of each signaling point includes a telephone user part (TUP) 1 performing functions for telephone signaling processing and exchange access control, etc., and an ISDN user part (ISUP) 3 for providing a circuit switching service and a supplementary service for voice and non-voice applications of an ISDN (Integrated Services Digital Network). The protocol structure further includes a transaction capabilities (TC) part 5 for performing an exchange function and controlling functions of special centers (a database, a special facilities unit, an operation & maintenance center) regardless of circuit switching, a signaling connection control part (SCCP) 7 for making possible transmission of various signals and data besides the circuited line control signal, and a message transfer part (MTP) 9 for performing transmission of a signaling message. The TUP 1, ISUP 3, and SCCP 7 are MTP user parts, and the TC 5 is a SCCP user part.
To provide an additional service, the SCCP 7 performs efficient transmission of signaling information between an exchanger and an exchanger, or between an exchanger and a database not having a direct bearing on a circuited processing. For example, when a service is performed by utilizing a database of a remote service control point placed apart from an exchanger, the SCCP 7 supplements a function of the MTP 9 in order to efficiently transmit a non-circuit related signal required for an inquiry and a reply about a database between the exchanger and the service control point.
A signaling transfer point among signaling points of the No.7 signaling network may not have a protocol stack such as the TUP 1, the ISUP 3, the TC 5, etc.
In the No.7 signaling network, a method for routing a signaling message received from the SCCP TC 5 to a destination signaling point is generally divided into two types. One is a routing by a sub-system number (SSN) and a signaling point code (SPC), and the other is a routing by a global title (GT).
FIG. 3 illustrates an example of a format of an address indicator of a SCCP signaling message format. As depicted in FIG. 3, an address indicator of a SCCP signaling message is 8 bits, and it includes a point code indicator, a SSN indicator, a GT indicator, a routing indicator, and a bit reserved for national use.
The point code indicator indicates whether a valid point code (signaling point code) is recorded on an SCCP signaling message and the SSN indicator indicates whether a valid SSN is recorded on the SCCP signaling message. The global title indicator indicates whether a valid global title is recorded on the SCCP signaling message and a type of the global title when a valid global title is recorded. The routing indicator indicates a routing method of the SCCP signaling message.
Accordingly, using the routing indicator of the address indicator of the signaling message, a signaling message routing method of the No.7 signaling network is determined. When the routing indicator indicates routing by a global title, the signaling message is routed by the routing method according to the global title.
A global title is an address constructed with digits such as a telephone number. It is a major part of a signaling message used for permitting an indirect routing other than by an address of a destination signaling point in a signaling network.
Because the MTP 9 is a lower layer protocol of the SCCP 7, it can route a signaling message only by a SSN and a signaling code. In order to perform the routing by a global title, a global title translation (GTT) has to first be performed. The GTT is used to map a global title included in a signaling message into a SSN and a signaling point code recognizable by the MTP 9. GTT is performed in the SCCP 7.
FIG. 4 illustrates an embodiment of a related art global title translation apparatus in a No.7 signaling network. The global title translation apparatus is typically provided in the SCCP 7.
As shown in FIG. 4, the related art global title translation apparatus in the No.7 signaling network includes a general GTT module 20 performing global title translation by referring to a global title translation database (not shown in FIG. 4) when a signaling message routed by the global title is received.
To transmit an SCCP signaling message from signaling point A to signaling point F using the global title routing function, the GTT can be divided into three types according to a global title translation point. In the first type, global title translation is performed at an originating signaling point (signaling point A). In the second type, global title translation is performed at a signaling transfer point (signaling point B, C, D, or E). In a third type, a first global title translation is performed at an originating signaling point (signaling point A) and a second global title translation is performed at a signaling transfer point (signaling point B, C, D or E).
A global title translation type is generally predetermined in construction of a signaling network, and an administrator of a signaling network maintains and manages global title translation information according to a global title translation type by using a translation database.
In order to transmit a signaling message from signaling point A to signaling point F, the SCCP TC 5 of an originating signaling point (signaling point A) transmits a signaling message to the SCCP 7 of a destination signaling point. Then, a general GTT module 20 of a global title translation apparatus of the SCCP 7 translates a global title included in a received signaling message by referring to a global title translation database of the originating signaling point. The SCCP 7 transmits the received signaling message to the MTP 9, and the MTP 9 transmits the signaling message to a pertinent signaling point in order to transmit the signaling message to a signaling point code as a result value of the global title translation.
The related art No. 7 signaling network has various problems. For example, in the related art No. 7 signaling network, because an administrator of a signaling network has to maintain and manage all global titles used in a signaling network in a global title translation database, transmission of a signaling message by using a routing function according to a global title is intricate when a large quantity of global title translation data exists.
In addition, because global title translation data of each signaling point is maintained and managed according to a predetermined global title translation type, in the related art global title translation apparatus in the No.7 signaling network, whenever a change of a global title translation type is required, an administrator of a signaling network has to change a global title translation database every time. Accordingly it is difficult to change a global title translation type of a signaling network.
Additionally, in the related art global title translation apparatus in the No.7 signaling network, because a global title translation database has to be retrieved in order to find a signaling transfer point, a global title translation function is performed only at a signaling transfer point. Thus, much time is consumed in a signaling message processing, and system performance is lowered.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.